The technical field of this disclosure is semiconductor manufacturing methods, particularly, a method for molding light emitting diode lamps.
Recent improvements in lighting technology have developed white solid-state lamp technology based on the use of ultraviolet and blue GaN/InGaN light-emitting diodes (LEDs). This technology offers the exciting potential of highly efficient low voltage lighting sources that are rugged, highly reliable, and inexpensive. For highly industrial countries, the potential energy savings are very significant. In the U.S., about 20% of all electricity and about 7.2% of all energy is used for lighting. Energy savings also can result in environmental improvements by lowering the emissions from coal or oil fired power plants. Low voltage solid-state lighting also offers the opportunity to take advantage of local power sources, reducing the need for expensive power grids. Low voltage solid-state lighting offers a wide range of new lighting sources and products, including distributed panel lighting, conformable lighting systems, and intelligent lighting schemes.
A white solid-state lamp can be obtained by coating a conventional light-emitting diode with a phosphorescent material, such as coating LEDs of GaN/InGaN-based epitaxial structures with phosphor. The phosphor absorbs the diode emission of blue or UV light and re-emits a broad band of yellow-green or red and green light. The re-emitted light combines with the original unabsorbed blue light to produce a white light.
The commercial technique typically employed in phosphor deposition on LEDs involves the use of phosphor powders blended in a liquid polymer system, such as epoxy resin, polypropylene, polycarbonate, or silicone. Generally, a small amount of the phosphor-impregnated epoxy is painted or dispensed on the LED die, then dried or cured. A clear epoxy lens is then constructed around the die, although the phosphor-impregnated epoxy can be used to construct the whole LED lens. Other techniques have also included dusting phosphor powders or spray painting phosphor powder liquid mixtures directly on the LED die.
FIGS. 1A and 1B show schematic diagrams of a typical surface mount technology (SMT) white light LED lamps. FIG. 1A shows an SMT LED lamp manufactured by a pre-dip process. The LED chip 40 is disposed on and electrically connected to metal contact base 42 having a reflector cup 44. A phosphor epoxy coating 46 containing phosphor particles 48 fills the reflector cup 44 and covers the LED chip 40. An epoxy lens 50 is molded over the phosphor epoxy coating 46. The phosphor epoxy coating 46 is often irregular because it is dropped or painted onto the LED chip 40. Although the phosphor epoxy coating 46 is disposed close to the LED chip 40 for efficient light production and the epoxy lens 50 can be clear so as not to interfere with light transmission, variability of phosphor concentration and geometry in the phosphor epoxy coating 46 causes color and light transmission inconsistencies between different LED lamps.
FIG. 1B, in which like elements share like reference numbers with FIG. 1A, shows an SMT LED lamp manufactured by a pre-mix process. Phosphor epoxy lens 52 containing phosphor particles 48 fills the reflector cup 44, covers the LED chip 40, and forms an optical dome 54. Although the large volume of the optical dome 54 produces consistent color, the disposition of the phosphor particles 48 throughout the whole phosphor epoxy lens 52 interferes with the light transmission making the LED lamp inefficient.
Current phosphor deposition methods are inefficient in production and less than optimum in result. The resulting white solid-state lamps may lack color repeatability and uniformity, so as to be unsuitable for color-critical applications. The lamps are inefficient and convert less of the chip radiation into visible light than possible due to phosphor placement away from the light emitting diode, and absorption and reflection in binder materials. In addition, the current phosphor deposition methods are difficult to translate into mass production for coating many single diodes and for coating large arrays of diodes mounted on circuit or ceramic boards.
It would be desirable to have a method for molding light emitting diode lamps that would overcome the above disadvantages.
The present invention allows efficient, cost effective manufacturing of LED lamps by producing arrays of LED lamps in a single batch. The present invention also produces a better, more efficient LED lamp with consistent color and light transmission. The molding process controls the shape and mixture consistency of the phosphorescent material and controls the lens shape for the desired light transmission characteristics.
One aspect of the present invention provides a method for molding light emitting diode lamps by providing a light emitting diode (LED) chip and a first mold insert. The first mold insert defines a first mold void, which is located about the LED chip. Light converting material is injected into the first mold void and the first mold insert is then removed from about the LED chip. A second mold insert defining a second mold void is provided, and the second mold insert located about the light converting material. Lens material is injected into the second mold void.
Another aspect of the present invention provides a system for molding light emitting diode lamps. The system comprises a mold frame, a first mold insert locatable in the mold frame and defining first mold voids locatable about the LED chips, a second mold insert locatable in the mold frame and defining second mold voids, and an injector to inject light converting material into the first mold voids and to inject lens material into the second mold voids.
One aspect of the present invention provides a method for molding light emitting diode lamps by providing light emitting diode (LED) chips and first mold inserts. The first mold insert defines first mold voids and the first mold voids are connected by first runners. The first mold voids are located about the LED chips and light converting material is injected into them. The light converting material forms light converting moldings on the LED chips and forms first runner trails in the first runners. The first mold insert is removed from about the LED chips. A second mold insert is provided. The second mold insert defines second mold voids locatable over the light converting moldings. The second mold voids are connected by second runners locatable over the first runner trails. The second mold voids are located about the light converting moldings and lens material is injected into them.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention, rather than limiting the scope of the invention being defined by the appended claims and equivalents thereof.